I have been reading about UASBs (Upflow Anaerobic Sludge Blankets), but have not found a detailed manual of how to design and build one.
Is there such a manual available on the internet?

I am especially interested in placing UASBs upstream of Vegetated Sand Filters, as a means of getting as much of the suspended solids out as possible and converting these solids into useable biogas. I am thinking about domestic wastewater and slaughterhouse wastewater. Even without the artificial wetland, a stand-alone UASB would be much, much better than the existing straight pipes to the rivers.

UASBs seem especially applicable here in the Amazon, where the soils are mostly all clay, so a 5-meter-deep reactor could be readily dug down into the ground and then the walls could get reinforced with ferrocement, bricks, concrete blocks, or something. This would also apply in much of the Andes, where there is a thick layer of compressed volcanic ash that also allows for deep digging. By being below ground, this should allow them to be gravity-fed.

Maybe you go for the very simple Anaerobic Baffled Reactor (ABR), which do not need deep digging. In simple terms an ABR is "only made" out of a settler and at least 4 UASBs in line. An ABR do not need any external power supply and pump if at least a small gravity of 20-30 cm is available.

On susana.org you can find drawings of an ABR made from concrete. But avoid just "Copy and Paste".

Even in cold European climate we made good experiences with our own small prefab ABRs made from PE, for domestic use (6 - 30 p.e.). Conservative COD reduction approx. 50% during winter and 70-80% during summer. Unfortunately our costly permission costs involved (approx. 14,000 EUR for permission per plant)in regard to German gas safety regulations, do not allow the customers to use the biogas out of small scale ABR-plants.

I had recently the same problem, it seems that UASB is pretty spread in south america but not so much around europe.
From what I gathered at the time with old collegues, with UASB you're gaining a lot of volume (5h MRT against 1 day MRT for ABR) but you need to extract the sludge every week or so because the little hoses of the inlet pipe (bottom of the system) can get clogged quickly if sludge isn't pumped out regularly. On another hand, I'd be curious about the Gas production with MRT so short. If you find some interesting publications available, please share it I'd be very interested.

Sanitary engineer with base in Brazil and Peru, doing consultancy in other countries of LA

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Hi Chris,
when I started to design UASB I worked my way through the basic book by V Haandel and Lettinga
Anaerobic sewage treatment: a practical guide for regions with a hot climate. For me it was excellent as it discusses lots of design principals, of assumptions today there might me much more sophisticated books, but I like the in-depth approach. You have to see that the book is from 1994, so there are new developments but comparing what has been build here in Brazil (where we have lots of UASB) to what is described, you can see that the technology has not changed that much. Some of the following 4 aspects in the book are often underestimated and the description in the book makes it seem easier than it is:
• Problems with flow distribution
• Problems with scum build up
• Problems with sludge removal
• Problems with sealing the gas chamber to avoid venting
These aspects often led to failure.
I would recommend to be very, very careful and to have a look at a series of reactors while designing, they seem to be simple but they are tricky. Good pre-treatment is absolutely crucial.
But yes, UASBs are a very good, effective method of bringing down BOD for warm climates without the use of energy but generating energy, as well for domestic wastewater.

We are currently involved in the first project for larger biogas use from UASB in Brazil where we will generate 190 kW of electricity using the gas from the UASB (a plant with about 150 l/s). Later in the year we will report on that.

Thanks for this info and congratulations on your successes with UASBs in Brazil.

Is the Van Haandel and Lettinga book available somewhere on the internet?
Is there a time after which it would be legal to copy a book and post it on the internet (given this book is from 1994)?
Could this sort of book be posted on SuSanA.org?

How much scum and grease floats to the top? Does this flow continuously somewhere? Or does it get removed periodically?

What is the range of depths of your UASBs in Brazil? It seems that the deeper it is, the more water pressure and the more anaerobic. Or is this my imagination?

What pre-treatment do you do? I think of UASBs as pre-treatment before Vegetated Sand Filters.

Do your UASBs flow by gravity? Or are electric pumps used to have constant flows?

AguaVerde, thanks for the info on ABRs, but why do you consider these better than UASBs, aside from not having to dig so deep? In places like here in Amazon, the soil is often clayey and not hard to dig.

Short answer, because of its simplicity in system and functionality ("low-tech") under harsh condition, as mentioned in text-books and based later on my own local experiences even in the cold climate too.

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Dear Chris,
some quick answers…as I learned today that long answers are in the danger of not beeing read .
• Maybe you did not see that I put the link for the book books.google.com.br/books?id=MB1SAAAAMAA...qi=2&redir_esc=y
(to the forum organizers – I find it difficult as well to see if there is a link or not)
• I have no idea about copy rights, but good parts are readable in google books.

“How much scum and grease floats to the top? Does this flow continuously somewhere? Or does it get removed periodically?“

Too much, especially in a slaughter house if you don´t have a very effective grease removal

Does this flow continuously somewhere? Or does it get removed periodically?

That is the problem. The flow to “somewhere” is not easy to solve, therefore most leave it on, resulting in very thick layers of scum which might as well block the gas. Manual cleaning is the most common but therefore you have to open the reactor and the gas goes off. We are working on solutions but there is no recipt.

What is the range of depths of your UASBs in Brazil?

UASB for domestic wastewater are in the range from 4,5 – 6 m of depth.

It seems that the deeper it is, the more water pressure and the more anaerobic. Or is this my imagination?

That is your imagination, the better process has nothing to do with the depth, it has to do with upflow velocity (to have the minimum “sludge blanket” (as from the name UASB Upflow Anaerobic Sludge Blanket)). It you have a very high velocitiy you get problems in the decantation, if you have a too low velocity you have a septic tank. Therefore large flux variations are a crucial point.

What pre-treatment do you do? I think of UASBs as pre-treatment before Vegetated Sand Filters.

Good screening is crucial to be able to distribute the wastewater by triangular weirs (if you are planning to do that), Sand removal is crucial as the sand fills up the reactor with the time and it forms a very hard mass together with the organic matter, which is not possible to be pumped out, Grease removal is crucial due to the reasons sited above. There fore I don´t use UASB for plants smaller than15.000 pe (just a rough number). My personal choice is: 5-50 pe. Septic tank, 50 – 2.000 p.e baffled reactor (ABR), 2.000 – 15.000 it depends, > 15.000 UASB.

Do your UASBs flow by gravity? Or are electric pumps used to have constant flows?

I did both already, no general idea.

I hope that helped. Just two more remarks. From a security in construction standpoint it does not sound too good to me to dig a hole with 5m depth and the idea of ferro cement for sure does not work. You need a VERY (sorry Jürgen I´m a fan of trolls and of capital letter use at for me it is a way to express what I think is important without doing anything else – just referring to another post at the forum here) good quality cement as there is strong H2SO4 corrosion.

I did see the link you put in your long message, but I did not express 100% clearly that I am looking for a version I can READ on the internet and not just buy (which requires credit cards, time, etc.) I have not found any part of this book in Googlebooks, and your first link says "Kein E-Book verfügbar", the second link says "Nenhum e-book disponível", which I suspect both mean "no e-book available".

OK. So ferrocement is ruled out due to the H2SO4. What about a brick and cement mortar lining for the tank? What if we make a lining from PET plastic Coke bottles? (I have a couple of methods in mind for such a recycled PET lining.)

What do you make the hood for catching the gas out of? I was thinking of ferrocement, but that is ruled out. What about replacing the steel wires with non-corrodable plastic and adding latex into the cement?

I am a student of water, trying to keep our treatment designs 'as simple as possible but not simpler'.

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Hi, Canaday--

You mentioned in this thread you have ideas regarding making (impervious?) wall liner out of PET plastic, as in Coke liter bottles. How might one seal such cut-out plastic to make an impervious liner? If practical this would be very useful for many other 'container' applications.
Regardez, Taber, Wetlands Work! Cambodia

It is nice to hear from you. Are you still in Cambodia? How are your wetlands?

I presume PET plastic bottles would be much more impervious to the acids in a biogas reactor, such as the UASB, as compared to cement, steel or a mix of the two (ferrocement). I also presume that the liner would not have to be watertight, especially where the soils are water-saturated clay or where rivers, wells, etc. are over 16 meters away, plus suspended solids in the water should be expected to plug the spaces in the surrounding soil.

The two methods I have in mind are labor-intensive, although not terribly so. The first involves cutting the straight, cylindrical sections of 3-liter, which easily open out flat, like shingles. Holes can be perforated with hot metal and, then, the "shingles" can be woven together.

The second involves making columns of PET bottles of any size, which then get woven together with strips of the same PET plastic. The columns can then be filled with soil or cement.

Seems to me like that wouldn't give sufficient structural strength to avoid collapse, and since it is leaky it can not be used for a cover of a ferrocement structure.

Epoxy coats of cement structures are generally a good solution against H2S and other chemical corrosion in sewer pipes, so that is probably a suitable solution.

For lower tech / cheaper solutions... hmm maybe a tar coat would work if reapplied from time to time?
Otherwise...probably not suited for the huge size, but in-situ burned ceramics have also been used for bigger water storage containers, and might be an option.